Refrigeration



March 5, 1963 A. c. SCHNEIDER ETAL 3,079,763

v REFRIGERATION Filed Jan. 25, 1962 2 Sheets-Sheet 1 w n H m ATTORNEYS March 5; 1963 A. c. scHNElDER ETAI. 3,079,763

REFRIGERATION Filed Jan. 25, 1962 2 Sheets-Sheet 2 ATTORNEYS ant.

United States Patent nace h'jh atented Mar, 5, 1963 3,679,763 REFRIGERATION Anthony C. Schneider and Frederick L. Young, 31., York, Pa., assignors to Freezing Equipment Sales, lne., York, Pa., a corporation of lennsylvania Filed dan. 25, 1962, Ser. No. 168,638 o Claims. (Cl. 62-84) This invention relates to refrigeration systems, and more particularly to refrigeration systems employing staged compressors.

One problem frequently encountered in refrigeration systems of the compressor-condensor-evaporator type is that of removing compressor lubricant from the refrigerin staged compression systems it has been recogniled that the intel-stage cooler serves as an eiicient separator. However, since the cooler is not a lubricant puritier, it is necessary to treat the oil further (as by the application of heat) in order to remove the remaining refrigerant and render the oil suitable for re-use.

It is also known that the performance of staged refrigeration systems can be improved by cooling the low stage compressor. The art discloses many ways of cooling compressors but most require the use of expensive auxiliary equipment. Some, however, employ the refrigerant itself and simply allow a portion of the system charge to expand in the cooling jacket of the compressor. This method has met with some success but when used with rotary compressors of the Vane type certain .difficulties arise. The problem in this case is due to the fact that on shut-down, liquid refrigerant may condense in the cooling jacket, and on subsequent start-up this liquid vaporizes producing non-uniform cooling. As a result, seizure `ofthe rotor frequently occurs.

The object of this invention is to provide a method and apparatus for simultaneously purifying the lubricant and cooling the low stage compressor in a satisfactory manner. According to this invention, the lubricant, or more correctly the lubricant-refrigerant mixture, separated in the cooler is transferred'to the cooling jacket of the low stage compressor to maintain in that jacket a body of liquid in heat exchange relation with the compressor. The heat generated by operation of the compressor is transferred to the mixture in the jacket thereby driving the refrigerant from the lubricant and simultaneously cooling the compressor. The refrigerant so separated is transmitted from the jacket to the discharge flow from the low stage co.L pressor and the puried lubricant is withdrawn and returned to the lubrication circuit.

The preferred embodiment of the invention will now be described in detail with reference to the accompanying drawings in which:

FlG. l is a schematic .diagram showing a simplified refrigeration system incorporating the invention.

FIG. 2 is a sectional view taken on line 2-2 of FIG. l.

As shown in the drawings, the refrigeration system includes a rotary low stage compressor l1 of the vane type having suction and discharge connections l2 and 13, and a high stage compressor 14 of the reciprocating piston type. The discharge connection 13 leads the compressed refrigerant from the low stage compressor through a trap l to an interstage cooler 16 whence it is delivered by a conduit 17 to the high stage compressor 25.4. The fully compressed refrigerant gas discharged by the high stage compressor 14 ilows through a conduit 13 to a condenser 19 where it is liquiiied and discharged into a receiver 21. Liquid refrigerant is fed from receiver 2l to an evaporator Z2 through a conventional expansion valve (not shown) and the vaporized refrigerant leaving the evaporator is returned to the suction connection l2 of the low stage compressor.

'the interstage cooler lo is of a conventional commercially available type and includes a horizontal tank 23 containing a perforated pipe .24 that communicates with connection l5 and is immersed in a bath 25 of liquid refrigerant. The apparatus for cooling the refrigerant bath is not illustrated. The refrigerant used in this system, for example ammonia, has a lower specific gravity than the lubricant, which is oil, and therefore, the oil separated from the refrigerant in cooler 15 collects in a vertical depending leg 26. lnterstage cooler lo may also be a vertical tank, in which case leg 26 is simply the bottom portion of the tank.

Associated with the low stage compressor il is a lubrication circuit including an oil reservoir 27 the top of which is connected to compressor suction conduit 12 by conduit 39 and which supplies oil pump ZS, and branched conduits 29 and 3l that lead oil under pressure to the bearings, seal and other lubrication points of the compressor.

Compressor l1 is provided with a conventional cooling jacket 32 to which is connected a conduit 33 leading from the depending leg Zo of the cooler lo or the bottom of a vertical cooler. The refrigerant-contaminated oil fed to the jacket 32 through conduit 33 is maintained in heat exchange relation with the compressor l1 with the result that the compressor is cooled. The heat absorbed by the mixture 34 in jacket 32 drives o the entrained refrigerant which rises to the top of the jacket and is returned to the interstage cooler i6 through conduit 35'. The temperature of the refrigerant flowing through conduit 35 is indicative of the position of the liquid level 36 in jacket 32, and this level is maintained substantially constant by a thermostatically controlled valve 37 located in conduit 33. The thermometric bulb 38 connected with the valve actuator is fixed to conduit 35 and the actuating mechanism is so arranged that the valve 37 opens and closes as the temperature of the refrigerant in conduit 35 rises above and falls below a perdetermined value.

'it will be understood that maintenance of a constant liquid level in jacket 32 ar'fords a constant uniform compressor temperature.

The purified oil in jacket 32 has a higher specic gravity than the incoming contaminated oil and, therefore, it settles to the bottom of the jacket. This oil is withdrawn from the jacket and returned to reservoir 27 through a conduit 39. Flow through this conduit 39 is regulated by a second thermostatically controlled valve il that responds to the temperature in jacket 32 at a level above the connection with conduit 39. The temperature sensed by thermometric bulb 42 is indicative of the condition of the oil surrounding it inasmuch as the presence of vaporizing refrigerant at this level will lower the temperature of the bulb and the absence of such refrigerant will cause its temperature to rise. The valve 4l is set to open and close, respectively, as the temperature sensed by bulb 42 rises above and falls below a predetermined value selected to insure the presence of pure oil in the region around bulb 42. Since the cond-uit 39 withdraws oil from a point below the bulb, this arrangement guarantees that the oil conveyed to reservoir 27 is refrigerant free.

it sometimes happens, as a result of improper matching of refrigeration load to system capacity, that incomplete vaporization of refrigerant will occur in evaporator 22. This produces a condition commonly called wet compression, i.e., liquid refrigerant is delivered to and expands in compressor il. When this happens, the compressor "al does not generate suicient heat a purify the oil in jacket 32. As a safety measure, an auxiliary electrical heater i3 is installed in jacket 32 so that the puritication process can continue during periods of Wet compression.

It should be mentioned that although cooling of the rotary compressor 11 is accomplished by evaporation of refrigerant in jacket 32, this will not adversely aiect the compressor even during shut-down because of the presence of a substantial body of oil. The oil serves to diS- perse the refrigerant in the jacket 32, to reduce its evaporation rate and the rate of heat ow from the compressor and produce uniform temperature throughout the jacket.

As stated previously, the drawings and description relate only to a preferred. embodiment. of the invention. Since many changes ycan be made in the structure of `this embodiment without departing from the inventive concept, the following claims should provide the sole measure o f the scope ofthe invention.

What we'claim is:

1. In a staged refrigeration system having a low stage compressor with a cooling jacket, a high stage compressor, a cooler arranged to cool the compressed gaseous refrigerant'owing' from the low stage compressor to the high stage compressor, and a circuit for feeding` lubricant to the low stage compressor, the method of'separating lubricant from the refrigerant and coolingthe low stage compressor which comprises (r1) withdrawing from the coolerthe mixture of lubricant and refrigerant thatseparates from the-.compressed gaseous refrigerant;

(b) transferring the withdrawn mixture to the cooling jacket to maintain therein a quantity of this mixture in heat exchange relation with the compressor, whereby the refrigerant is driven from the mixture and the compressor is cooled;

(c) removing the separated refrigerant gas from the cooling jacket and returning itto the compressed refrigerant in the cooler; and

(d) removing the lubricant in the cooling jacket from which refrigerant has been separated and returning it to Vthe lubricantY circuit.

2. The method defined in clam-1 1V inl which. the lrate kof transfer of mixture from thev4 cooler to the cooling jacket is controlled indirect relation to thetemperature of the separated refrigerant'gasremovedfrom the jacket.

3.` The method defined in claim 1 in whichptheulubricant has a higher specific gravity than the refrigerant;

and in which the yoil removed from the jacket is taken from a point adjacent the bottom of the jacket when the temperaturel at a higher level in the jacket exceeds a predetermined value.

4. In a staged refrigeration system having a low stage compressor with a cooling jacket, a high stage compressor, an interstage cooler* located in a discharge line leading from the low stage compressor for cooling the compressed gaseousrefrigerant flowing to the high stage compressor, and a lubrication circuit. for feeding1ubricant to the low stage compressor, the combination of (a) a rst conduitV connecting the lubrication circuit with the cooling jacket at a point adjacent its bottom;

(b) a. second conduit connecting vthe cooling-jacket with the cooler at a point adjacent its bottom;

(c) a third conduit connecting. the interstage cooler with the cooling jacket at a point adjacent its top;

(d) rst valve meansV controlling flow through the. first conduitand .shiftable in opening andjclosing directions; and

(e) vmeans responsive to the temperatureof the liquid in the cooling jacket ata-level above'the connection with-the first conduit for opening-the rst'valvemeans when the temperature rises above aY given value and for closing that valveameans `whenthe temperature falls belowthat value.

5. The combinationdened in claim 4 including (a) second valvemeans controllingowthroughthe second conduit and shiftable inA openingfandclosing directions; and

(b) means vresponsive to the temperature in ,the thirdconduit` for openingand closing the secondvalve means respectivelyfas the temperature rises above and decreases belowa certain .valuet 6. The combination defined in claimS including auxiliary means forV heating the liquid;` in; thecooling jacket.

References Cited inthe tileY of, thismat'ent UNITEI) STATES PATENTS 2,178,425' Johnson Oct. 31,1939 2,677,944 Run May 11,1954 2,900,801 Honegger Aug.' 25, 1959 3,023,590 Playle Mar. 6, 1962 

1. IN A STAGED REFRIGERATION SYSTEM HAVING A LOW STAGE COMPRESSOR WITH A COOLING JACKET, A HIGH STAGE COMPRESSOR, A COOLER ARRANGED TO COOL THE COMPRESSED GASEOUS REFRIGERANT FLOWING FROM THE LOW STAGE COMPRESSOR TO THE HIGH STAGE COMPRESSOR, AND A CIRCUIT FOR FEEDING LUBRICANT TO THE LOW STAGE COMPRESSOR, THE METHOD OF SEPARATING LUBRICANT FROM THE REFRIGERANT AND COOLING THE LOW STAGE COMPRESSOR WHICH COMPRISES (A) WITHDRAWING FROM THE COOLER THE MIXTURE OF LUBRICANT AND REFRIGERANT THAT SEPARATES FROM THE COMPRESSED GASEOUS REFRIGERANT; (B) TRANSFERRING THE WITHDRAWN MIXTURE TO THE COOLING JACKET TO MAINTAIN THEREIN A QUANTITY OF THIS MIXTURE IN HEAT EXCHANGE RELATION WITH THE COMPRESSOR, WHEREBY THE REFRIGERANT IS DRIVEN FROM THE MIXTURE AND THE COMPRESSOR IS COOLED; (C) REMOVING THE SEPARATED REFRIGERANT GAS FROM THE COOLING JACKET AND RETURNING IT TO THE COMPRESSED REFRIGERANT IN THE COOLER; AND (D) REMOVING THE LUBRICANT IN THE COOLING JACKET FROM WHICH REFRIGERANT HAS BEEN SEPARATED AND RETURNING IT TO THE LUBRICANT CIRCUIT. 